"Nonlinearity"

This mathematical term is best described by Nassim in his book Fooled by Randomness by the concept of Sandpile effect.
Think of making a structure of beach sand. Keep on raising the structure with sand till the time it falls off. Now try to figure out the effect of that last grain of sand that would have brought about this fall. The one grain has that non linear effect on that complete structure.

Non linearity in life is something our brain always refuse to understand. All of us have small events in our lives which have transformational effects on it. This is what can explain that extra mile effort before which most of us give up. Those who don't reap benefits of nonlinearity in life.